Two unarmed police women shot dead in Manchester are believed to have been lured to their deaths using a bogus burglary report.
The two police officers were killed during a routine call-out which subsequently led to the arrest of a man wanted by Greater Manchester police.
PC Nicola Hughes, 23, and PC Fiona Bone, 32, both suffered fatal injuries in the incident in Tameside.
One of Britain's most wanted men, Dale Cregan, 29, has been arrested in connection with the killings, and two previous murders.
Police said today there was nothing in the burglary report that indicated armed officers would be required.
Greater Manchester Chief Constable Sir Peter Fahy named the "brave" officers this afternoon.
He said it appeared that someone had deliberately lured the officers to the scene.
He said the motive for the attack was “impossible to fathom”.
Following the attack, Dale Cregan, who was being hunted in connection with separate gun and grenade attack murders, handed himself in to a police station in Hyde, Greater Manchester.
Sir Peter paid tribute to the two officers, describing Hughes as a "great bobby", who was "always smiling".
He said Miss Bone, who had been planning her wedding, was an "excellent bobby" and a "calm, gentle woman".
Speaking at a press conference Sir Peter said the force was “absolutely devastated” by the deaths saying: “We are all shocked by what happened this morning.”
Sir Peter said he believed Cregan had been “protected by a criminal conspiracy to harbour him”, adding that the force was “fully determined” to investigate that conspiracy and bring those involved “to book”.
The Chief Constable said it was 'routine' to send unarmed officers to such calls.
“We believe that Dale Cregan was in a house in Abbey Gardens overnight, and at some point this morning has either himself has made a call or had somebody else make a call reporting a burglary,” Sir Peter said.
“This particular address was not known to us.
So as would be routine, two unarmed officers were sent to the scene.
Police said that one of the female officers died at the scene, the other was critically injured and died shortly afterwards.
Sir Peter continued: “Clearly we are devastated today by the loss of two of our officers.
“This is one of the darkest days in the history of the Greater Manchester Police if not for the police service overall, because we have lost two deeply loved and valued colleagues, because they are part of our team, policing is very much a family.
“But also because of the huge efforts that officers had been making to arrest and detain Dale Cregan. Obviously the officers involved in that inquiry are shattered by this outcome.”
Eyewitnesses reported that a hail of bullets were fired and that a grenade was used in the attack.
Window cleaner Warren Shepherd said: “I just heard gunshots, bang, bang, bang - around ten of them, then a pause and a big explosion.”
The killings are likely to reignite the debate over whether police officers should be armed.
Sir Peter said his force believed "passionately" that police should remain unarmed, despite the tragedy.
He said: "Clearly we are a police force that is routinely unarmed, although we have great expertise from armed officers in our support.
"We are passionate that the British style of policing is routinely unarmed policing. Sadly we know from the experience in America and other countries, that having armed officers certainly does not mean, sadly, that police officers do not end up getting shot."
Dale Cregan, who only has one eye, had been the subject of a huge manhunt after the murders of David Short, 46, and his son Mark, 23.
A £50,000 reward had been offered for information leading to his arrest.
David Short was killed at his home in Folkestone Road East, Clayton, Manchester, on August 10, while Mark was gunned down at the Cotton Tree pub in nearby Droylsden, on May 25.
Four men have already been charged in connection with Mark Short's murder and are due to enter pleas at Manchester Crown Court in November.
Prime Minister David Cameron said the killing of officers was "a shocking reminder of the debt we owe to those who put themselves in danger to keep us safe and secure".
Chairman of the GMP Federation Ian Hanson called the deaths "the slaughter of the innocents".
"I'm going to look beyond the uniform here. What we've got are two young girls that went out this morning and they've got an absolute right to come home tonight to their loved ones. This is cold-blooded murder. It's the slaughter of the innocents. GMP is a family.
"I'm struggling to find the words to use to officers out there who've lost friends and colleagues. It's a dark day for GMP, it's a dark day for policing, it's a dark day for society."